1. Technical Field of the Invention
The present invention relates in general to laser pattern imaging of workpieces in the manufacturing of products comprising patterning of a photosensitive surface employing a laser direct imaging device. More particularly, the present invention relates to methods and apparatuses for performing pattern alignment to components such as dies.
2. General Background of the Invention
It is common practice to manufacture printed circuit boards in a method to build a sequence of layers having different electric circuit patterns. For this purpose pattern generators using a laser direct writer as an imaging device for writing an electric circuit pattern on a substrate are well known.
General Description of Fan-Out Process
For example in the manufacturing of printed circuit boards with integrated circuits, a plurality of dies in the form of small blocks of semiconducting material each having a functional electronic circuit are distributed on a printed circuit board workpiece e.g. in the form of a carrier silicon wafer. The dies are then covered with further layers of material to form the integrated circuit in a series of manufacturing steps. In the course of the manufacturing process patterns are generated on selected layers of the workpiece in one or a plurality of patterning steps.
Pattern Generation
Patterns are generated on a layer of a workpiece, for example for the purpose of forming an electric circuit pattern generated in order to couple connection point's or contact pads of components such as dies in a desired electric circuit. The expression die is herein used as common expression for any electronic component such as a passive component, an active component, or any other component associated with electronics. Such a pattern is generated in a writing or printing process in which an image of a circuit pattern is projected, written printed on a surface layer covering a conductive layer on the workpiece.
In this context writing and printing are to be understood in a broad sense. For example, projecting, writing or printing a pattern on a surface may include exposing a photoresist or other photosensitive material, annealing by optical heating, ablating, creating any other change to the surface by an optical beam, etc.
Dependent on the used kind of photosensitive surface material, unexposed or exposed parts of the photosensitive surface layer are removed to form etching masks on the workpiece. The masked workpiece is then etched to form the desired electrical circuit pattern on the conductive layer. A variation of this concept is to use the pattern to deposit material onto the underlying layer, e.g. to form an electrical circuit pattern or connection points on the workpiece.
Pattern Generator
The pattern generator is for example realized by means of a laser direct imaging (LDI) system devised for writing a pattern on the photosensitive surface by means of a laser scanning the surface with a laser beam that is modulated according to image pattern data and forming an image representing a desired electrical circuit pattern.